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AbstractAbstract

[en] Perturbation theory is used to solve the problem of the precession of Mercury's perihelion, this phenomenon being a relativistic effect. The expansion parameter appears naturally when the orbit equation is written in an appropriate form and it completely justifies the use of the first order approximation. (author)

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 30(2); p. 341-346

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[en] In the present work it's shown the possibility of obtaining a pole-figure from the data generated in a conventional X-ray equipment, with a commercial goniometer and no electronic device to process the data. The way to plot the pole-figure on-line is by means of measuring the diffractogram and plot manually the stereographic projections. The atainable precision is very low in such a cumbersome process. In this paper we substitute such method by storing the data in a punched tape from a conventional teletype. The data is processed in a computer and the pole-figure is recorded by a plotter attached to the computer. (author)

Original Title

Evaluacion de la figura de polos

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Journal Article

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 30(2); p. 237-252

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[en] Partially summed perturbation series constitute one possible starting point for construction of theories of infinite and finite Fermion matter. I discuss various problems encountered in these theories like choice of single-particle potentials, zero-order states, summation of ring-and ladder-diagrams and occupation probabilities. (author)

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 28(1); p. 1-28

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[en] Perturbation theory of quantum mechanics and the method of images of electrostatics are used in a simple calculation of the F band position in the absorption spectra of a surface F center. The case of alkali-halides with the NaCl structure is considered. (author)

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Journal Article

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 28(1); p. 29-39

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[en] An extension of the Parameterized Post-Newtonian (PPN) formalism to third order in the expansion parameter m/r (where m = GM/c

^{2}denotes the mass of the source of the field and r the distance to its center) is used to derive analytical expressions accurate to the same order for the prediction of the experimental measurments of the frequency shift effect on electromagnetic signals travelling within the solar system. An experimental situation is considered for which it is seen that the consequences of including higher order terms are undetectable by present-day observations or experiments. Some deliberations on issues in the historic context in which the development of the relevant ideas took place is considered necessary to round this work out and is presented in an introductory section. (author)Primary Subject

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Journal Article

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 29(1); p. 113-128

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AbstractAbstract

[en] The goal of this article is to review the present status of the Interacting Boson Model (IBM) for describing the collective properties of medium and heavy mass nuclei, with particular emphasis being given to the work on the IBM at the University of Arizona. First, a concise review of the basic phenomenological IBM, as developed by Arima and Iachello for only one kind of boson, is presented. Next, the extension of the IBM to both proton and neutron bosons is outlined. This latter model is known as the IBM-2. The application of the IBM-2 to the tungsten isotopes by the University of Arizona group is discussed, followed by their calculations for the mercury isotopes. In the case of the mercury isotopes an extended form of the IBM-2 is developed in order to treat the configuration mixing of two entirely different structures which occur in the same energy region. The relationship between the bosons and the underlying fermionic structure of the nucleus is discussed using the generalized seniority scheme of Talmi. Work by the Arizona group to calculate the phenomenological parameters of the IBM-2 using these generalized seniority ideas is described, along with their results, which agree quite well with the empirical values. Efforts by the University of Arizona group to determine the influence of terms left out of the basic IBM, such as the g boson, using second-order perturbation theory are described. In conclusion, a discussion of the limitations as well as the usefulness of the IBM is given along with its exciting possibilities for the future of nuclear structure physics. (author)

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 27(4); p. 533-581

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AbstractAbstract

[en] The non equivalence between the macrosopic Maxwell equations and the Lienard-Wiechert equations is stressed. For stationary conditions (under which the equivalence is correct) an equation substituting the Lorentz-Dirac one is obtained. The new equation is absent of the paradoxes of the Lorentz-Dirac one and implies a decreasing in the electronic proper mass. It is suggested that the equilibrium in mass of the real electron follows from a balance between the mass lost by emission and the mass gained from the external field. (author)

Original Title

El electron cohete: consideraciones criticas sobre las ecuaciones de Lienard-Wiechert

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 26(1); p. 45-58

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AbstractAbstract

[en] We study the production of electron density waves by neutrinos propagating through a plasma. We treat this process in field theoretically as a Cherenkov emission of phonons (quanta of electron density waves) by neutrinos. The energy transferred to a supernova shock wave by phonon emission from neutrinos is a factor 2 x 10 times the corresponding energy deposited by plasmon (longitudinal photon) emission. (Author)

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Journal Article

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 48(1); p. 43-47

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AbstractAbstract

[en] It is shown in this paper that, using only common concepts of well known modern physics and quantum mechanics textbooks (as one- a two-electron atoms, perturbation theory), we can develop a simple and powerful method to calculate the binding energies of complex electron configurations, as well as ionization energies, X-ray levels, etc. (Author)

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Numerical Data

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 48(1); p. 76-87

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AbstractAbstract

[en] In this current study, we have undertaken vibronic intensity calculations for the absorptions ((

^{4}I_{15/2}) Γ_{k}) → ((^{4}I_{13/2}) Γ_{l}) of the Er^{3+}in the Cs_{2}NaErCl_{6}elpasolite type system. This system is extremely complicated to handle from both a theoretical and an experimental viewpoints. This theoretical work shows that over an energy range of about 400 cm^{-1}, a substantial amount of transitions are likely to take place (about 100 transitions; twenty five of them are magnetic dipole allowed and seventy five are vibronically allowed). It is then a formidable task to identify and assign all of these transitions in a non-ambiguous way. Also the experimental evidence available for these absorptions is related to a total of about twenty lines in the luminescence spectrum of this system. The spectrum itself is very challenging and the superposition of spectral features is most likely to occur. A careful analysis of the calculated vibronic intensities and overall oscillator strengths for the various transitions indicates that the current model used is both flexible and appropriate to deal with this kind of systems. In a forthcoming paper, we will examine the rather unusual high intensity associated with the ((^{4}I_{15/2}) Γ_{k}) → ((^{4}S_{3/2}) Γ_{l}) excitations. (Author)Primary Subject

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Journal Article

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Revista Mexicana de Fisica; ISSN 0035-001X; ; v. 47(3); p. 245-252

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